Thomas a



(No Model.) T. A. EDISON.

FILAMENT FOR INGANDESOENT LAMPS. I

No. 307,029 Patented Oct. 21, 1884.

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UNITED STATES PATENT OFFICE.

THOMAS A. EDISON, OF MENLO PARK, NEIV JERSEY, ASSIGNOR TO THE EDISONELECTRIC LIGHT COMPANY,

OF NEWV YORK, N. Y.

FILAMENT FOR INCANDESCENT LAMPS.

SPECIFICATION forming part of Letters Patent No.'30'7,029, dated October21, 1884.

' Application filed October 12, 1882. (No model.)

To all whom it may concern:

Be it known that I, THOMAS A. EDISON, of

Menlo Park, in the county of Middlesex and State of New Jersey, haveinvented a new and useful Improvement in Electric Lamps and theManufacture thereof, (Case No. 489,) of which the following is aspecification.

The object I have in view is to provide a simple and economical processof forming the carbon incandescing filaments of electric lamps, whichprocess shall produce flexible filaments of even density and resistance,whose shape shall conform approximately to that of the glass globeswhich I use with my lamps. Such process consists in first cutting from afibrous vegetable substance, preferably bamboo, a filament of somewhatmore than the desired size (to allow for contraction during carbonization) and having enlarged ends, then carbonizing said filament ina closed chamber, preferably under pressure or strain, or both, andfinally bending the flexible carbon filament thus produced into anydesired shape, preferably one approaching that of the lamp-globe, itsends being secured, either before or after bending, to metallic wires.By taking hold of both ends of the carbonized filament and bending it inthe middle it naturally assumes a shape approximating to that of alongitudinal section of the pear-shaped globe commonly employed by me,and this is the shape I prefer; but it is evident that the carbon may bebent into any other desired shape. The use of filaments of such shape ofcourse adds to the symmetrical appearance of the lamp, and, in addition,the filament being equally near to the glass in every part throughoutits length, the glass is more equally heated, and there is less dangerof breakage than with the form of filament hitherto in general use. Thecarbonizing-flasks used are of simpler construction, as, instead ofcurved grooves for holding thepreviously-bent filament, or blocks forholding it both at its ends and in the middle, a single straight grooveonly is necessary, or means for holding its ends alone. The process addsto the economy of manufacture of the lamp, for a larger number ofstraight filaments can be carbonized at the same time than of filamentspreviously bent. The carbonized filament is sufficiently flexible to bereadily bent into the proper shape.

In the drawings, Figure l is an elevation of a completed lamp containinga filament made according my process, and Fig. 2 a view of the filamentbefore bending.

The filament A is cut into the form illustrated in Fig. 2, and thencarbonized, after which it is bent as in Fig. 1, its ends secured tometallic wires a 0, preferably by the electro-deposition of metal uponthe joints, and the whole placed within the inclosing-globe B, which isafterward exhausted of air and sealed off at b.

\Vhat I claim is- The process of forming the flexible incandescingfilaments of electric lamps, consisting in first forming a straightfilament of carbonizable substance, then carbonizing the same, andfinally bending the flexible filament thus formed into the desiredshape, substantially as set forth.

This specification signed and witnessed this 9th day of October, 1882.

Tl-IOS. A. EDISON.

Witnesses:

H. W. SEELY, E. H. PYAT'I.

